watchOS 9 is the ninth release of watchOS, shipped September 12, 2022, with the Series 8 and the new Ultra. It was the serious-athlete release: Workout gained heart-rate zones, custom structured intervals, triathlon auto-transitions, running form metrics (vertical oscillation, stride length, ground contact), and race-route pacing — the feature set that let the Ultra face Garmin credibly. Health deepened in parallel with AFib History's burden tracking and the Medications app's logging and interaction warnings.

Workout zones, custom workouts, triathlon support, and running dynamics; AFib History; Medications; sleep stages; the Lunar and Metropolitan faces; Low Power Mode (Series 4 and later, delivered with the cycle); and international roaming for cellular models.

watchOS 9 armed the Ultra's assault on the sports-watch market and moved the health story from alerts to management — burden, medication, stages — the chronic-care framing later releases (Vitals, Training Load) extended.